3-methylenetetrahydrofurans and 3-methylenepyrrolidines by addition of 2-(bromozincmethyl)-2-alkenyl ethers or 2-(chloromagnesiomethyl)-2-alkenyl ethers to aldehydes, ketones and imines followed by pd(0)-catalyzed cyclization
作者:Jaap van der Louw、Juul L. van der Baan、Henk Stichter、Gerardus J.J. Out、Franciscus J.J. de Kanter、Friedrich Bickelhaupt、Gerhard W. Klumpp
DOI:10.1016/s0040-4020(01)92280-x
日期:1992.11
Reaction of 2-(bromozincmethyl)-2-alkenyl ethers 1 or 2-(chloromagnesiomethyl)-2-alkenyl ethers 2 with aldehydes, ketones and imines affords the addition products 4 and 8, which undergo Pd(0)-catalyzed cyclization to the 3-methylenetetrahydrofurans 6 (R1 = H) and 3-methylenepyrrolidines 10 (R1 = H). Addition of 1a or 1b to α,β-unsaturated substrates proceeds in the 1,2-mode only. Reaction of the 3-alkyl
2-(溴锌甲基)-2-烯基醚1或2-(氯镁金属甲基)-2-烯基醚2与醛,酮和亚胺的反应提供加成产物4和8,它们经过Pd(0)催化的环化反应3-亚甲基四氢呋喃6(R 1 = H)和3-亚甲基吡咯烷10(R 1 = H)。将1a或1b添加到不饱和的α,β底物中仅以1,2-模式进行。3-烷基衍生物1c,d,e和2b的反应几乎在所有情况下导致支链加成产物4或8。在闭环的条件下,4或8(M = ZnBr)不稳定并异构化为相应的线性加成产物13或17。与4(M = ZnBr),Pd(0)催化环化比异构化成13更快,因此允许四氢呋喃6的区域特异性和立体选择性形成。在的情况下,8(M = ZnBr),但是,异构化至17比闭环更快,因此,钯(0) -催化的环化导致的环化产物的混合物10,19和20。支链加成产品4衍生自镁化合物2b的化合物8和8在闭环的条件下是稳定的,从而允许区域特异性和立体选择性地制备四氢呋喃6(R